This invention relates generally to a socket having means to make electrical connection with leads of an electronic device received in the socket and more specifically to a socket having electrical contact elements which, in connection with the insertion of a semiconductor integrated circuit package (which will hereafter be referred to as an IC package), makes electrical contact by biasing the contact elements against leads of the IC package and to a socket which is suitable for IC package testing, in particular, electrical property testing.
A conventional socket for use in test apparatus for testing various electrical properties of an IC package is shown in FIG. 1. Contacts 101 are fixedly mounted on both sides of a main socket body 92. A fixed body portion 102 of each contact 101 has a U-shape with a bar shaped flexible portion 103 extending upwardly from the center of the body portion thereof. A wide contact portion 105 is provided at the tip of flexible portion 103 for engagement with a lead of an IC package. A terminal leg 106 protrudes from the lower side of the fixed body portion 102 and extends through the bottom wall of main socket body 92 and is received through a bore of a printed circuit substrate (PCB) 30 of the test apparatus (not shown in the drawing) to fixedly mount socket 91 to PCB 30.
IC package 21 has generally J-shaped leads 26 on both right and left sides as seen in the figure, and is supported by a head 31 which has been provided in the test apparatus in such a manner as to be able to move in alternating opposite directions. IC package 21 is mounted in main socket body 92, as shown in the figure, as a result of forward movement of head 31.
In this position, leads 26 push contact portions 105 of contacts 101 outwardly toward the right and left sides respectively. As the flexible portions 103 of the contacts are elastically deformed, the contact portions 105 press against leads 26 by the spring return force thereby making an electric connection. In this manner, leads 26 of IC package 21 are connected to a prescribed electrical circuit in the test apparatus through contacts 101 and PCB 30.
The procedural steps for mounting the IC package in the socket are shown in FIGS. 2(a)-2(d) with only the left side being shown as a cross section since both sides are symmetrical. FIG. 2(a) shows the socket prior to mounting the IC package in the socket. FIG. 2(b) shows the structure when the lead of the IC package has just engaged the contact portion; FIG. 2(c) shows the structure when the contact portion 105 slides on the lead of the IC package and FIG. 2(d) shows the structure when the IC package is fully mounted in the socket as head 31 has reached the prescribed mounting position.
Going from FIG. 2(a) to FIG. 2(b) there is no bending of the contact flexible portion 103, with contact portion 105 exerting no force against lead 26. Going between the FIGS. 2(b) and 2(c) positions, the flexible portion 103 is bent with contact portion 105 pressing against the lead 26 and this pressing force increasing from zero in FIG. 2(b) to a prescribed pressing force shown in FIG. 2(c). Going between the FIGS. 2(c) and 2(d) positions, the pressing force remains constant at the prescribed level.
The IC package has its electrical properties tested in the position shown in FIG. 1 and FIG. 2(d). The time required for testing one IC package is in the range between several seconds to a minute. The IC package is mounted in the socket, tested and removed from the socket to make place for the next IC package to be mounted in the socket for testing.
The socket according to the prior art was designed for use in a heat resistance test of the IC package. In this test, called a burn-in test, the package is heated and held in the mounted state at a prescribed temperature for a selected period of time and its electrical properties are tested. Contact force between respective contacts and leads is high for electrical property testing and, in view of the fact that there are a very large number of repetitions of the mounting and dismounting of IC packages in such electrical property testing, a small amount of solder which peels off the solder-plated layer of the lead of the IC package accumulates on the contact portion. This accumulation tends to adhere to the lead of a subsequent IC package received in the test apparatus, thereby contributing toward the lowering of product quality. In addition, flexible portion 103 of the contact tends to loose its spring contact force, thereby creating a problem in terms of the durability of the socket.
It is an object of the invention to provide a socket which overcomes the noted deficiencies of the prior art and which obtains the desired level of contact force of the contact elements against the leads of the electronic device when the mounting of the electronic device is completed, which decreases sliding of the contact elements against leads at a time when the required high level pressing force is maintained, prevents the lowering of the product quality of the electrical part stemming from this pressing force and which has improved durability.
Briefly, in accordance with the invention, a socket comprises contact elements which are electrically connectable, when in a compressed state, to respective electrical parts, such as the leads of an IC package mounted in the socket, and an operating member which has been movably mounted on the main body of the socket in such a way as to operate by pressing the contact elements against the respective electrical parts at the completion of the mounting of the electrical part in the socket.
According to a feature of the invention, at the time of mounting of the electrical part by the electrical part mounting means (such as, for example, head 31 which will be described later) the operating member presses the contact elements in dependence upon the movement of the electrical part mounting means.
According to another feature of the invention, the electrical connection between the contact elements and the electrical parts are effected by flexibly bending the contact elements by the pressing of the operating member which is journaled on the main body of the socket in such a manner as to be freely rotatable, one end of the operating member being engaged by the electrical part mounting means and the other end of the operating member pressing a contact element.
According to yet another feature of the invention, each contact element is bent back into a generally U-shaped configuration. The electrical part is inserted at a prescribed position aligned with a position between the bight of the U-shaped contact element and one free end thereof, the other end of the contact element being fixed to the main body of the socket. The free end of the contact element is engaged with the operating member, and the electrical part is compressively engaged by a respective contact element proximate to the engagement location.
Preferably, according to the invention, a plurality of the combinations of the operating member and the contact elements are provided in the main socket body in such a way as to face each other, with the electrical part being mounted between the plurality of combinations.
The socket made in accordance with the invention is such that the electrical part mounting means is provided on the electrical part testing apparatus and is capable of moving in alternating opposite directions relative to the main body of the socket and is preferably used as a socket for the electrical part test apparatus.
Various additional objects and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.